This invention pertains generally to microwave phase discriminators, and particularly to a type of microwave phase discriminator fabricated using four identical directional couplers. It is possible to configure these couplers so that microwave signals may pass therethrough without encountering discontinuities or short circuits.
It is known in the art that a microwave phase discriminator may be used in many applications, such as in sidelobe cancellers, cross-polarization generators and instantaneous frequency and bearing monitors. A microwave phase discriminator for any such an application may be made up of a microwave bridge network, a plurality of square-law detectors and a pair of differential amplifiers to produce two signals representative of the phase difference between two input signals.
It is known that compensation for some channel-to-channel imbalances may be effected by commutating, or switching, pairs of signals between the two signal channels so that an averaging process may be applied. Thus, within a conventional microwave phase discriminator, commutation may be implemented by double-pole double-throw switches before each diode pair arranged periodically to reverse the signals applied to the diodes, and additional double-pole, double-throw switches before the inputs of each one of the differential amplifiers. Obviously, providing such switches and the requisite control circuitry complicates the design of the phase discriminator. Even when such commutation is effected, adequate compensation is difficult to achieve because of any imbalances existing in the switches.